α-Hemoglobin stabilizing protein (AHSP) markedly decreases the redox potential and reactivity of α-subunits of human HbA with hydrogen peroxide.

摘要: α-Hemoglobin stabilizing protein (AHSP) is a molecular chaperone that binds monomeric α-subunits of human hemoglobin A (HbA) and modulates heme iron oxidation subunit folding states. Although AHSP·αHb complexes autoxidize more rapidly than HbA, the redox mechanisms appear to be similar. Both metHbA isolated met-β-subunits undergo further in presence hydrogen peroxide (H(2)O(2)) form ferryl species. Surprisingly, much lower levels H(2)O(2)-induced are produced by free met-α-subunits as compared with met-β-subunits, no detected H(2)O(2)-treated AHSP·met-α-complex at pH values from 5.0 9.0 23 °C. Ferryl species were similarly not AHSP·met-α Pro-30 mutants known exhibit different rates autoxidation hemin loss. EPR data suggest protein-based radicals associated state exist within HbA α- β-subunits. In contrast, treatment H(2)O(2) yields smaller radical signals, when added AHSP·α-complexes. AHSP binding also dramatically reduces potential α-subunits, +40 -78 mV 1 m glycine buffer, 6.0, 8 °C, demonstrating independently has higher affinity for Fe(III) versus Fe(II) α-subunits. Hexacoordination complex markedly decreases rate initial reaction thus provides protection against damaging oxidative reactions.